When in vitro fertilization (IVF) was first developed, fresh embryo transfer was the only type of transfer that was available. This is mainly because the cryopreservation technology was still underdeveloped.
After decades of research, the first embryo was successfully transferred using cryopreservation techniques and advanced reproductive technologies. This type of preserved embryo transfer is called frozen embryo transfer.
When patients undergo IVF, they face confusion between choosing fresh embryo transfer or frozen embryo transfer. This choice should not be made mainly based on timing; they should also consider other factors like success rate, emotional well-being, and overall outcomes.
This blog will help you understand the differences between these two methods and help the patients make informed decisions according to their needs and situations.
Understanding embryo transfer
The last step of IVF is embryo transfer. It mainly involves transferring embryos into the uterus after they have been fertilized and cultured in the laboratory. The transfer timing and condition of the uterus are important for the success of pregnancy.
In IVF, eggs will be taken from the ovaries and fertilized with sperm in a controlled environment. The resulting embryo will be cultured for a few days until it reaches the blastocyst stage, which is considered optimal for transfer.
Before the transfer, the uterus will be maintained and prepared for receiving the embryo. The uterine lining needs to be receptive to the embryo for implantation.
It is important to identify the timing of embryo transfer. Fresh embryo transfer normally takes place a few days after the egg is retrieved and the blastocyst stage is obtained. It occurs when the fertilized eggs are transferred into the uterus of women in the same IVF cycle in which eggs are retrieved and fertilized.
Meanwhile, in the frozen embryo, transfer timing can be flexible allowing for optimal synchronization with the uterine environment. In the case of frozen embryo transfer, the embryos are frozen after fertilization and can be stored for transfer in the later part of the IVF cycle.
The difference between fresh and frozen embryo transfers
Fresh embryo transfer
Fresh embryo transfer normally takes place 3 to 5 days after egg retrieval. They are fertilized with sperm in the laboratory, which results in the formation of embryos. This process must be monitored closely.
The main advantage of fresh embryo transfer is that there is a short time to pregnancy since there is only a 5-day waiting period between the retrieval of the egg and embryo transfer into the uterus. Also, many insurance companies do not cover the cryopreservation cost, so some patients will choose fresh embryo transfer because of financial reasons.
There are also some contraindications for using fresh embryo transfer. That is, if the progesterone level of the patient is increased, then fresh transfer cannot be done as it will affect the embryo implantation negatively. Similarly, if the patient has a high risk of experiencing hyperstimulation from the medications that are used for ovulation induction, the transfer of a fresh embryo will be dangerous for the patient.
Frozen embryo transfer
The frozen embryo transfer process can be done anytime the patient wishes. After the patient is ready for the transfer, they will be given medications that can act like a natural cycle, and the frozen embryo transfer date will be coordinated according to the cycle for optimization of implantation.
Frozen embryo transfer is needed if the patient likes to check for genetic abnormalities in embryos. Shortly after the retrieval of eggs, preimplantation genetic testing will be carried out.
A small sample of the embryo will be taken, and that sample with the DNA of the embryo will be assessed for chromosomal and genetic abnormalities. After the preimplantation genetic testing, embryologists can choose the chromosomally normal embryos for transfer. The rate of pregnancy success can be improved by transferring healthy embryos.
Frozen embryo transfer can also be used for subsequent pregnancy even after years since the embryos can be stored indefinitely. Also, if the patient likes to preserve fertility because of age, cancer treatment, or any other reasons, embryos can be preserved for later use, and when ready, frozen embryo transfer can be performed.
Success rates for fresh and frozen embryos of transfers
Various studies show a higher success rate when using frozen embryos than fresh embryos during embryo transfer. Some of the studies are,
New England Journal of Medicine: In a study published in 2018, it has been identified that women with infertility issues that are related to polycystic ovarian syndrome have higher live birth rates when frozen embryo transfer is carried out.
British Medical Journal: In the study carried out in 2020. It has been identified that there are no high ongoing pregnancy or live birth rates in women who are using frozen embryo transfer. This is mainly based on the patients having regular periods and through gonadotropin-releasing hormones.
Maternal age: A study has also identified that high-quality and healthy embryos can be used on older women for embryo transfer. There are no adverse effects on the implantation or live birth rates.
Fresh vs. frozen blastocyst transfer
The embryos that are developed for 5 to 6 days after fertilization are called blastocysts. The transfer of blastocysts, whether they can be frozen or fresh, can lead to a high rate of success when compared to the transfer of younger embryos. This is because they are close to the stage at which the implantation occurs naturally in the body.
Why is frozen embryo transfer better?
Various studies suggest that frozen embryo transfer has several advantages over fresh embryo transfer, including lower rates of preterm labor and higher birth weights. Along with that, the frozen transfer cycle will allow the body to recover in stimulation, which leads to a more favorable environment for implantation. Some other advantages are,
- Frozen embryo transfer typically costs less compared to fresh embryo transfer.
- Frozen embryo transfer can help preserve your fertility and help you plan for pregnancy when you are ready.
- It will give less mental and physical stress to the body of the woman.
- Frozen embryo transfer normally mimics the natural cycle.
- A frozen embryo cycle can also be used to check the gender and any genetic abnormalities in the embryo.
In various studies, it has been identified that live birth rates were slightly higher in frozen embryo transfer when compared to fresh embryo transfer. Also, frozen embryo transfer may provide a slight advantage in a successful pregnancy.
Conclusion
Going through IVF treatment can be challenging, but if it is filled with knowledge and guided by a trusted professional, it can help you to make an informed decision that can best suit your situation.
Whether you select fresh embryo transfer or frozen embryo transfer, always remember that each journey for parenthood is unique.
Factors include patient age, health conditions, uterine readiness, and personal preferences.
FET may involve longer waiting periods, which can be emotionally challenging for some patients.
Insurance coverage for FET varies, and some plans may not cover the costs of cryopreservation.
Yes, FET can be timed to coincide with a patient’s natural cycle for optimal results.
